var arr = [1,1,'11','11']

function unique(arr) 
{
    let res = []
    for(let i = 0; i < arr.length; i++) {
        var current = arr[i]
        if(res.indexOf(current) == -1) {
            res.push(current)
        }
    }
    return res
}
console.log(unique(arr) );